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Climate and Construction: 1.5 million homes in 10 years, but at what carbon cost?

John Bleasby
Climate and Construction: 1.5 million homes in 10 years, but at what carbon cost?

Ontario Premier Doug Ford is seeking re-election partly on the back of a promise to build more homes faster than ever before.

It’s a great campaign pledge, ready-made for the media. His promise of 1.5 million new homes over 10 years means a lot of construction. It’s a pledge heard in other parts of the country too, as politicians leverage housing supply versus demand to their advantage.

The problem arises when attempting to reconcile such ambitious promises against concurrent pledges to address GHG and carbon emission reductions. Building processes and operations not only result in carbon emissions but exert a heavy upfront embodied carbon price related to the materials used.

The issue is well addressed by Larry Strain, principal at Siegel & Strain Architects based in Emeryville Calif. In his paper, Time Value of Carbon, Strain explains carbon emissions are cumulative and that carbons emitted today are more critical than carbons emitted in the future.

Strain also discusses the balance between reducing operational carbons through net-zero energy ambitions that deliver benefits over time versus carbons associated with construction that occur in the immediate term.

“Embodied emissions now make up a much larger percentage of total lifetime emissions. Embodied emissions are also important because of when they occur — they are the first emissions from a new building. When a building is constructed — before it starts operating and generating operating emissions — it is already responsible for tons of GHG emissions.”

That’s why the spectre of embodied carbon raises its head when provincial and federal leaders suggest  the quick fix for the country’s proclaimed affordable housing crisis is the rapid construction of new homes.

Unfortunately, Canada’s latest model building code does little to definitively move the carbon issue forward, particularly as adopted in middling form by provinces such as Ontario. In any case, such codes only address energy efficiency through their mildly implied code improvements to envelope design and execution. Nothing is said about embodied carbon.

That shouldn’t prevent affirmative action by builders who truly wish to address the issue of embodied carbon directly and forcefully.

For example, U.K. builder St. Modwen Homes completed two carbon-negative homes at its new affordable housing development south of London.  

These timber frame homes are not only energy efficient in design and operation but use low-carbon concrete as foundations. As a result, they are capable of delivering a 125 per cent overall reduction in CO2 emissions compared to identical homes built to code standards.

“As an industry leader in using low-carbon modern methods of construction already, we have a responsibility to use this experience to prove that carbon negative houses can significantly cut energy bills and reduce emissions,” said Dave Smith, managing director, St. Modwen Homes. “Over the course of this year, we will be analyzing the results of this latest trial to aid us in our objective to build these new homes at scale for the benefit of homeowners and the environment.”

It’s worth noting that St. Modwen Homes is a significant player in U.K. housing, with operations across England and Wales. The company is owned by the Blackstone Group, a global investment management firm with assets over US$40 billion.

Closer to home is the newly announced BEAM embodied carbon calculator developed by Chris Magwood of Builders for Climate Action based in Peterborough, Ont. and available at no cost.

BEAM focuses on providing details of the embodied carbon impact of materials, key to reducing the upfront carbon emissions referred to by Strain. The software helps builders make choices from “a comprehensive list of all the available materials for all the main assemblies and the carbon footprint for each choice.”

It’s quick and easy to use, allowing builders to compare materials, match their carbon footprints to pre-determined climate goals and thereby create whole-house baselines and alternatives.

Promising 1.5 million homes is easy. Delivering them with minimal carbon impact is harder. However, builders can make that happen through their own initiative.

 John Bleasby is a Coldwater, Ont.-based freelance writer. Send comments and Climate and Construction column ideas to

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